Customers being charged a higher rate for electricity this month because of changes to Duke Energy’s billing cycle will get a refund on their next bill, officials with the utility announced Wednesday.

Following a rash of criticism from state lawmakers in Pinellas County and questions by the Public Service Commission, Duke’s Florida President Alex Glenn apologized to customers whose rates were “unintentionally” increased because their extra power use during a lengthened billing period pushed them into a higher price bracket.

The company is rerouting meter readings for hundreds of thousands of customers across the state to make the process more efficient, resulting in a one-time change in billing days.

Some customers will have fewer days on their bill, but those with extra days could see their energy use exceed 1,000 kilowatt hours, which drives the standard rate of $11.34 per 100 kilowatt hours up to $13.70.

“We apologize for any hardships and confusion we have caused our customers, and we will make this right,” Glenn said in a written statement. “We will continue to work with impacted customers until all credits have been issued. We are also taking steps to ensure that this does not happen again.”

About half of Duke’s 650,000 customers in Pinellas County have received bills during the change in the meter reading cycle, but not all of them will be eligible for a credit on their next bill.

Only customers whose usage exceeded 1,000 kilowatt hours because of the additional days will get a credit, company spokeswoman Nicole LeBeau said.

Duke is working to change its billing system to prevent outgoing bills from including the higher rates, but some customers may still be charged extra and will get a credit at the end of the next period, she said.

The company estimates the average credit will be around $5.50.

“People are using their air conditioning 24 hours a day as it is now anyway. A lot of folks are already in that higher tier just based on their usage,” LeBeau said.

State Sen. Jack Latvala, R-Clearwater, and state Rep. Dwight Dudley, D-St. Petersburg, have written letters demanding that Duke cease charging customers extra due to its billing changes.

Dudley wrote a letter Tuesday to Florida House Speaker Will Weatherford suggesting a special committee be formed to investigate the billing practices.

“I don’t believe that it is any coincidence that they have decided to make these changes during the hottest month of the year when customers use the most energy,” Dudley said in a written statement.

The PSC has called on Glenn to discuss the matter in Tallahassee on Sept. 4.

Customers with concerns about their bill should contact Duke at 800-700-8744, 7 a.m.- 9 p.m. Monday through Friday.